The carbon-nitrogen ratio (COD/NH4(+)-N) is an important factor affecting nitrification and denitrification in wastewater treatment; this factor also influences nitrous oxide (N2O) emissions. This study investigated two simulated intermittently aerated semi-aerobic aged refuse bioreactors (SAARB) filled with 8-year old aged refuse (AR). The research analyzed how differences in and the combination of influent COD and NH4(+)-N impact N2O emissions in leachate treatment. Experimental results showed that N2O emissions increased as the influent COD/NH4(+)-N decreased...

While the most likely structure of the active site in iron-containing zeolites has been recently identified as [FeO](2+) (Snyder et al. Nature 2016, 536, 317-321), the mechanism for the direct conversion of methane to methanol over this active species is still debatable between the direct-radical-rebound or nonradical (concerted) mechanism. Using density functional theory on periodic systems, we calculated the two reaction mechanisms over two d(4) isoelectronic systems, [FeO](2+) and [MnO](+) zeolites. We found that [FeO](2+) zeolites favor the direct-radical-rebound mechanism with low CH4 activation energies, while [MnO](+) zeolites prefer the nonradical mechanism with higher CH4 activation energies...

Application of manure has been recommended as an effective strategy to to mitigate climate change. However, the magnitude of greenhouse gases emission derived by application of manure to agricultural soils across environmental conditions still remains unclear. Here, we synthesized data from 379 observations in China and quantified the responses of soil nitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4) emissions to manure (Org-M) in comparison to chemical fertilizers (Min-F) or non-fertilizers (Non-F)...

We report a data-set of CO2, CH4, and N2O concentrations in the surface waters of the Meuse river network in Belgium, obtained during four surveys covering 50 stations (summer 2013 and late winter 2013, 2014 and 2015), from yearly cycles in four rivers of variable size and catchment land cover, and from 111 groundwater samples. Surface waters of the Meuse river network were over-saturated in CO2, CH4, N2O with respect to atmospheric equilibrium, acting as sources of these greenhouse gases to the atmosphere, although the dissolved gases also showed marked seasonal and spatial variations...

Microorganisms with the capacity to reduce the greenhouse gas nitrous oxide (N2O) to harmless dinitrogen gas are receiving increased attention due to increasing N2O emissions (and our need to mitigate climate change) and to recent discoveries of novel N2O-reducing bacteria and archaea. The diversity of denitrifying and nondenitrifying microorganisms with capacity for N2O reduction was recently shown to be greater than previously expected. A formerly overlooked group (clade II) in the environment include a large fraction of nondenitrifying N2O reducers, which could be N2O sinks without major contribution to N2O formation...

Obtaining high quality syngas from sewage sludge (SS) means transferring a low-grade SS into a high-grade fuel or raw materials for chemical products. In this study, Fe is added to SS in form of Fe2(SO4)3 to produce an effective and self-sufficient catalyst in order to obtain more syngas and minimize liquid products from SS pyrolysis. The Fe-embedded sewage sludge chars (SSCs) were used as catalysts for volatile reforming at 600°C. It has been found that the gas yield increases from 15.9 to 35.8wt% of the SS and that of liquids decreases from 31...

Silver nanoparticles (AgNPs) are the most common materials in nanotechnology-based consumer products globally. Because of the wide application of AgNPs, their potential environmental impact is currently a highly topical focus of concern. Nitrification is one of the processes in the nitrogen cycle most susceptible to AgNPs but the specific effects of AgNPs on nitrification in aquatic environments are not well understood. We report the influence of AgNPs on nitrification and associated nitrous oxide (N2O) production in estuarine sediments...

The goal of this study was to investigate the effectiveness of a membrane-aerated biofilm reactor (MABR), a representative of counter-current substrate diffusion geometry, in mitigating nitrous oxide (N2O) emission. Two laboratory-scale reactors with the same dimensions but distinct biofilm geometries, i.e., a MABR and a conventional biofilm reactor (CBR) employing co-current substrate diffusion geometry, were operated to determine depth profiles of dissolved oxygen (DO), nitrous oxide (N2O), functional gene abundance and microbial community structure...

The denitrification efficiency of woody biomass as carbon source is low because of its poor carbon availability. In this study, representative poplar sawdust was pretreated with lime and peracetic acid to enhance the biomass digestibility to different degrees; sawdust was then mixed with soil to investigate its denitrification efficiency. Under controllable conditions (25-95°C, 12-24h, varying dosages), sawdust digestibility (characterized by reducing sugar yield) was selectively enhanced 1.0-21.8 times over that of the raw sawdust (28...

A sludge treatment reed bed system (STRB) is a technology used for dewatering and stabilising sewage sludge via assisted biological mineralisation, which creates a sludge residue suitable for use as fertiliser on agricultural land. We evaluated the effect of sludge residue storage time (stabilisation time) for three STRBs on soil N mineralisation and CO2 and N2O emissions in soil. The experiment revealed that the N mineralisation rate and emissions of CO2 and N2O decreased as a function of treatment time in the STRBs...

Solid state fermentation is a promising technology however rising concerns related to scale up and reproducibility in a productive process. Coffee husk and a specialized inoculum were used in a 4.5L and then in 50L reactors to assess the reproducibility of a cellulase and hemicellulase production system. Fermentations were consistent in terms of cellulase production and microbial communities. The higher temperatures achieved when operating at 50L generated a shift on the microbial communities and a reduction of nearly 50% on cellulase production at pilot scale...

Euro VI emission standards for heavy-duty vehicles (HDVs) introduced for the first time limits for solid particle number (PN) and NH3 emissions. EU regulation also includes a Portable Emissions Measurement System (PEMS) based test at type approval, followed by in-service conformity (ISC) testing. A comprehensive study on the real-time on-road emissions of NOx, NH3, N2O and PN from a Euro VI HDV equipped with a Diesel Oxidation Catalyst (DOC), a Diesel Particle Filter (DPF), a Selective Catalytic Reduction (SCR) system and an Ammonia Oxidation Catalyst (AMOX) is presented...

Flavo-diiron proteins (FDPs) are non-heme iron containing enzymes that are widespread in anaerobic bacteria, archaea, and protozoa, serving as the terminal components to dioxygen and nitric oxide reductive scavenging pathways in these organisms. FDPs contain a dinuclear iron active site similar to that in hemerythrin, ribonucleotide reductase, and methane monooxygenase, all of which can bind NO and O2. However, only FDP competently turns over NO to N2O. Here, EPR and Mössbauer spectroscopies allow electronic characterization of the diferric and diferrous species of FDP...

One-electron reduction of [Fe(NO)-(N3PyS)]BF4 (1) leads to the production of the metastable nonheme {FeNO}(8) complex, [Fe(NO)(N3PyS)] (3). Complex 3 is a rare example of a high-spin (S = 1) {FeNO}(8) and is the first example, to our knowledge, of a mononuclear nonheme {FeNO}(8) species that generates N2O. A second, novel route to 3 involves addition of Piloty's acid, an HNO donor, to an Fe(II) precursor. This work provides possible new insights regarding the mechanism of nitric oxide reductases.

Relatively low nitrogen (N) efficiency and heavy environmental costs caused by excessive N fertilizer applications with outdated fertilization techniques are current cultivation production problems with maize among smallholders in North China Plain. Although many studies have examined agronomical strategies for improving yields and N use, the integrated effects of these measures and the associated environmental costs are not well understood. We conducted a 2-year field study with two densities (67,500 plants ha(-1), which was similar to local farmers' practices, and 90,000 plants ha(-1)) and three N rates (0, 180, and 360 kg ha(-1), the rate local farmers' commonly apply) to test the integrated effects for maize production at Wuqiao experimental station in North China Plain...

While it is clear that biochar can alter soil N2O emissions, data on NO impacts are scarce. Reports range from 0 to 67% soil NO emission reductions postbiochar amendment. We use regional air quality and health cost models to assess how these soil NO reductions could influence U.S. air quality and health costs. We find that at 67% soil NO reduction, widespread application of biochar to fertilized agricultural soils could reduce O3 by up to 2.4 ppb and PM2.5 by up to 0.15 μg/m(3) in some regions. Modeled biochar-mediated health benefits are up to $4...

Nitrogen non-point pollution and greenhouse gas (GHG) emission are major challenges in rice production. This study examined options for both economic and environmental sustainability through optimizing water and N management. Field experiments were conducted to examine the crop yields, N use efficiency (NUE), greenhouse gas emissions, N losses under different N and water management. There were four treatments: zero N input with farmer's water management (N0), farmer's N and water management (FP), optimized N management with farmer's water management (OPTN) and optimized N management with alternate wetting and drying irrigation (OPTN+AWD)...

Atmospheric carbon dioxide (CO2) concentrations is continuing to increase due to anthropogenic activity, and geological CO2 storage via carbon capture and storage (CCS) technology can be an effective way to mitigate global warming due to CO2 emission. However, the possibility of CO2 leakage from reservoirs and pipelines exists, and such leakage could negatively affect organisms in the soil environment. Therefore, to determine the impacts of geological CO2 leakage on plant and soil processes, we conducted a greenhouse study in which plants and soils were exposed to high levels of soil CO2...